Engine Control - EPROM to Improve Driveability Problems
18-48Amended
4/98
DATE: 5/95
MODEL:
XJS (4.0L) 1995 MY
VIN:
194775-197549
Uneven Cold Idle - Drivability Enhancements - ECM Upgrade
Remove and destroy Bulletin 18-48, dated 5/95. Replace with this Bulletin.
ECMs are no longer sent to Lucas since EPROMs are now available for upgrading ECMs at the dealer.
ISSUE:
1995 MY XJS 4.0L vehicles within the above VIN range may display the following symptoms:
SYMPTOMS
Uneven idle following cold start.
Inconsistency at cruising speeds of 50 - 60 mph (80-100 km/h). Hesitation at low speed, low throttle application with a warm engine. These symptoms result from an unfavorable combination of fuel volatility and ignition timing factors. The ECM EPROM has been revised to correct these conditions from VIN 197550.
ACTION:
If customers complain of the symptoms listed above on vehicles within the quoted VIN range and all other engine parameters are within specification, the ECM will require upgrading.
To upgrade an ECM to the latest specifications, follow the procedure as described below.
IMPORTANT
Inspect the vehicle to determine if a revised air pump hose with a vacuum bleed has been installed. If the existing air pump hose has no vacuum bleed, replace the hose with the correct revised hose for the vehicle.
Refer to Service Bulletin 18-47 for the appropriate part numbers and warranty information.
PREPARATION
1. Connect the PDU to the vehicle and check for any DTCs stored in the ECM.
2. Record any DTCs found on an OBDII report form (S-93), then clear them from the system. Any DTCs found must be diagnosed separately.
3. Turn the ignition OFF Wait 20 seconds, then disconnect the vehicle battery.
REMOVING ECM
1. Remove the carpet from the right side footwell.
2. Remove the ECM cover insulation pad.
3. After removing the mounting nuts, remove the cover from the ECM.
4. Remove the ECM from its mounting, disconnect both harness multi-plugs and remove the ECM from the vehicle.
REPLACING PROM
ECM tools required:
^ One Anti-static work mat, Part No. JAG 205/ST010
^ One PROM removal tool, Part No. JAG 999/ND
^ One TX 20 Torx Tamper-proof screw bit, JAG 20/TORX
CAUTION!
The following steps should only be carried out while working at an anti-static workstation (Illustration 1) and wearing a grounding wrist strap.
1. Position the ECM on the anti-static work mat so that when facing the multi- plugs, the red multi-plug is at the upper right and the black multi-plug to the lower left.
2. Note the position of the top cover with its mounting tab to the ECM housing. Mark both the cover and the casing using a felt tip marker to assist reassembly. Remove the four tamper resistant retaining screws of the top cover (the cover adjacent to the red multi-plug) using a Torx 20 Anti-Tamper screw bit.
3. Obtain a wooden block approximately 6 x 6 x 1 inches. Remove the seven retaining screws of the printed circuit board (Illustration 2). Lift the printed circuit board and support it on the wooden block so that no strain is applied to the ribbon connectors. Allow a clearance space so that no damage can occur from contact with the mounting brackets.
4. Remove the appropriate PROM covers by lightly gripping the PROM cover with a pair of pliers and using a side to side rocking action.
5. Use a suitable chip removal tool to carefully remove both PROM chips from the printed circuit board (Illustration 3). The PROM removal tool supplied may differ from that shown in the illustration.
6. Before installing the new microchip(s), identify the semicircular cutouts in both the chip and the socket on the printed circuit board (Illustration 4). The two cutouts must be aligned as the chip is inserted into the socket.
NOTE:
To aid in installing the PROM, an installation tool can be sourced at a local electronics supply store.
Careful manual alignment and installation methods must be used at this point in the procedure.
7. Identify and install the replacement 28-pin chip from the kit into the 28-pin socket and the 32-pin chip into the 32-pin socket.
CAUTION
The microchip MUST lie parallel to the printed circuit board with all the pins engaged into the socket (condition A, Illustration 5). Permanent damage to the chip is likely in conditions B or C. Malfunctions will occur with partial engagement as in condition D.
8. Install the original cover(s) over the PROM chip(s).
9. Carefully fold the printed circuit board back into its original location on the housing of the ECM. Make sure the multi-plug is correctly aligned with its location in the housing. Install the seven retaining screws. Torque the screws to 20 - 25 lb. in. (2.25 - 2.82 Nm).
10. Install the ECM cover on the housing aligning the marks made during disassembly. Install the four mounting screws. Torque the screws to 20 - 25 lb. in. (2.25 - 2.82 Nm).
11. Apply the PECUS label from the kit to the cover near the existing labels without covering them (Illustration 6).
12. Install the ECM by reversing the removal procedures.
13. Connect the battery and reset the vehicle clock.
14. Start the vehicle and perform an adequate road test to verify proper engine operation. Only if a drivability complaint exists, use the PDU to check the orientation of the oxygen sensors and to perform the engine setup.
PARTS INFORMATION
WARRANTY INFORMATION